Networks incorporating resistor-capacitor (RC) configurations are widely used in integrated circuit (IC) applications such as filters, phase-locked loops, frequency-based current references, and others. In general, the time constant of an RC-configured network is a determining factor in the performance of the network and its related circuitry. For example, the time delay and bandwidth of an RC-configured network are directly affected by its time constant. Therefore, any deviations in the specified time constant of such a network may adversely affect its functional parameters as well as those of its associated circuitry. The stability of a network time constant can be of particular importance when a relatively high level of precision performance is desired. However, time constant deviations in the approximate range of 20% to 25% can occur for a number of reasons, such as inconsistencies in IC manufacturing processes, IC supply voltage variations, environmental temperature changes, and the like.
Various tuning schemes have been employed to compensate for typical time constant deviations in IC applications. These tuning schemes have included the use of active elements and/or circuits within the network configuration that can be adjusted (tuned) to correct for detected variations in time constant values. Other types of tuning schemes have been based on the use of external networks that mimic the time constant of the actual network and provide a corrective reference for variations in the actual network. However, tuning schemes such as these typically require the use of external analog voltages, and also generally involve a relatively high part count in the external tuning and calibration circuitry. As such, the attainable tuning accuracy of a network is generally limited by the complexity of the external tuning and calibration circuitry.
Accordingly, it is desirable to provide a built-in (on-chip) self-test capability for automatically compensating RC time constant deviations that may be caused by factors such as fabrication processes, supply voltage variations, temperature changes, and the like. In addition, it is desirable to provide a built-in automatic tuning capability with relatively high precision that does not require external circuitry. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.